Irritability and movement of plant organisms. Irritability and movements of organisms Irritability and types of cell stimuli

The simplest forms of irritability are observed in microorganisms (bacteria, single-celled fungi, algae, protozoa).

In the example with the amoeba, we observed the movement of the amoeba towards the stimulus (food). This motor reaction of unicellular organisms in response to irritation from the external environment is called taxis. Taxis is caused by chemical irritation, which is why it is also called chemotaxis(Fig. 51).

Rice. 51. Chemotaxis in ciliates

Taxis can be positive and negative. Let's place a test tube with a culture of ciliates-slippers in a closed cardboard box with a single hole located opposite the middle part of the test tube, and expose it to light.

After a few hours, all the ciliates will concentrate in the illuminated part of the test tube. This is positive phototaxis.

Taxis are characteristic of multicellular animals. For example, blood leukocytes exhibit positive chemotaxis towards substances secreted by bacteria, concentrate in places where these bacteria accumulate, capture and digest them.

Irritability in multicellular plants. Tropisms. Although multicellular plants do not have sensory organs or a nervous system, they nevertheless clearly exhibit various forms of irritability. They involve changing the direction of growth of a plant or its organs (root, stem, leaves). Such manifestations of irritability in multicellular plants are called tropisms.

Stem with leaves show positive phototropism and grow towards the light, and the root - negative phototropism(Fig. 52). Plants respond to the Earth's gravitational field. Pay attention to the trees growing along the mountainside. Although the soil surface has a slope, trees grow vertically. The response of plants to gravity is called geotropism(Fig. 53). The root that emerges from a germinating seed is always directed downwards towards the ground - positive geotropism. A shoot with leaves developing from a seed is always directed upward from the ground - negative geotropism.

Tropisms are very diverse and play a large role in plant life. They are clearly expressed in the direction of growth in various climbing and climbing plants, such as grapes and hops.

Rice. 52. Phototropism

Rice. 53. Geotropism: 1 – a flower pot with straight-growing radish seedlings; 2 – a flower pot placed on its side and kept in the dark to eliminate phototropism; 3 – the seedlings in the flower pot have bent in the direction opposite to the action of gravity (the stems have negative geotropism)

In addition to tropisms, plants exhibit other types of movements - Nastia. They differ from tropisms in the absence of a specific orientation to the stimulus that caused them. For example, if you touch the leaves of a bashful mimosa, they quickly fold longitudinally and fall downwards. After some time, the leaves return to their previous position (Fig. 54).

Rice. 54. Nastia at the shy mimosa: 1 – in normal condition; 2 - when irritated

The flowers of many plants respond to light and humidity. For example, a tulip's flowers open in the light and close in the dark. The dandelion's inflorescence closes in cloudy weather and opens in clear weather.

Irritability in multicellular animals. Reflexes. Due to the development of the nervous system, sensory organs and organs of movement in multicellular animals, the forms of irritability become more complex and depend on the close interaction of these organs.

In its simplest form, such irritation occurs in coelenterates. If you prick a freshwater hydra with a needle, it will shrink into a ball. External irritation is perceived by a sensitive cell. The excitement that arises in it is transmitted to the nerve cell. The nerve cell transmits excitation to the skin-muscle cell, which reacts to irritation by contracting. This process is called reflex (reflection).

Reflex- This is the body’s response to irritation carried out by the nervous system.

The idea of ​​a reflex was expressed by Descartes. Later it was developed in the works of I.M. Sechenov and I.P. Pavlov.

The path traversed by nervous excitation from the organ that perceives the irritation to the organ that performs the response is called reflex arc.

In organisms with a nervous system, there are two types of reflexes: unconditioned (innate) and conditioned (acquired). Conditioned reflexes are formed on the basis of unconditioned ones.

Any irritation causes a change in metabolism in cells, which leads to excitation and a response occurs.

The main forms of manifestation of irritability in organisms are various types of motor reactions that are carried out by the whole organism or its individual parts. Obviously, only with the help of movement can an organism or organ expediently change position, optimize its position in space, avoiding the effects of unfavorable factors or, conversely, effectively use their beneficial effects.

The most common motor reactions of living organisms to changes in environmental conditions are taxis, muscular movements, and in plants (except taxis) - tropisms, nasties, nutations and autonomous movements.

Taxis are movements of a whole, independently existing, unicellular or multicellular organism, manifested in its spatial movement relative to the stimulus (movement of protozoa, algae). Depending on the nature of the body’s response, taxis can be positive when the movement occurs in the direction of the acting factor, and negative when the movement occurs in the opposite direction.

Taxis are classified depending on the type of stimulus: phototaxis, chemotaxis, thermotaxis. An example of a positive phototaxis there may be oriented movement of flagellated unicellular algae to the zone of optimal illumination, orientation of chloroplasts in the mesophyll cells of the leaf, chemotaxis- accumulation of bacterial cells near a lump of food, movement of leukocytes towards the bacterium, etc., thermotaxis- accumulations of unicellular organisms in the zone of optimal temperature.

A necessary condition for irritability is the reversibility of partial changes in structural proteins, the restoration of their previous state. In general, representatives of the animal world are specific from the point of view of irritability, since they lead an active lifestyle, have special organs of movement on a muscle basis, a nervous system with analyzers, and have complex forms of irritability - instinct, conditioned and unconditioned reflexes.

A change in the spatial position of the organs of a plant organism can be carried out: 1) due to the uneven growth of individual parts of the organ; 2) due to temporary changes in the permeability of the cytoplasm of cells, which in most cases leads to a decrease in their turgor pressure and, accordingly, to a change in the position of the organ. The active movements of the plant organism are also based on the phenomena of irritability and contractility of proteins in the cytoplasm of plant cells, which are combined with growth and other processes.

The directional orientation of organs and parts of plants in space is an important adaptation that allows them to most effectively use sources of food, water, light and at the same time protect themselves from the adverse effects of various factors.

Tropisms are the motor response of plant organs and parts to the unilateral influence of environmental factors - light, gravity, water, chemicals, etc. Depending on the nature of the response of the plant organism, tropisms can be positive and negative.

Geotropism is the growth response of individual plant organs to the unilateral influence of gravity. There are three types of geotropism: positive- when the organ grows vertically downwards, negative- when the direction of movement is opposite, i.e. upward and transverse, or diageotropism,- when the organ tries to take a horizontal position. The main tap roots are, as a rule, characterized by positive geotropism; branches of the first order of woody plants, stems of monocots, as well as petioles of leaves of many plants - negative; many rhizomes, lateral roots, lateral branches of some conifers, root hairs - transverse.

Of particular interest is the study of growth processes and the phenomena of geotropism under conditions of weightlessness. The absence of gravitational influence on the studied plants during long space flights on board orbital stations usually caused disordered growth of higher plants, as well as its premature cessation. If conditions are created that partially compensate for the absence of the gravitational factor (one-way illumination, electric current, artificial gravity, etc.), the growth and development of plants are normalized, as evidenced by the formation of seeds in experimental Arabidopsis plants during the long flight of astronauts V.V. Lebedev and A. N. Berezova in 1982

Phototropism. A sign of this type of movement is a clearly expressed positive or negative reaction of organs and parts of plants to unilateral exposure to light.

Under natural conditions in open areas, phototropism, as a rule, is not clearly manifested, since in addition to direct sunlight, the plant is exposed to a relatively strong scattered radiant flux from the sky and clouds. With one-sided exposure to light (near buildings, in a room), the phototropism of individual shoots, even the entire above-ground part, is especially clearly manifested - the plants seem to be drawn to the light.

In the long process of evolution, plant organisms are constantly in the field of action of the earth's magnetism and, of course, respond to the influence of the magnetic field. This type of motion is called magnetotropism. An example of this is the increased growth of roots oriented towards the south pole of the Earth or an artificial magnet.

Other physical and chemical factors can also have a one-sided effect on growing organs. Accordingly, they distinguish: chemotropisms, hydrotropisms, thermotropisms, traumatotropisms (i.e., the classification of tropisms depends on the natural source of irritation). The most indicative is the chemotropism of the roots, as a result of which an effective search and absorption of mineral nutrition elements from the substrate is carried out.

Nastya. Nastic movements include movements that are a response of organs or parts of a plant to the action of stimuli that do not have a specific direction, but affect diffusely and evenly from different directions.

Depending on the direction of movement and the nature of the influencing factor, nastic movements are classified as epinasty - downward bending of an organ (usually a leaf) due to accelerated growth or turgor stretching of the upper side of the base of the petiole (lowering of leaves of mimosa, white acacia).

Hyponastia is an upward bending of the organ due to accelerated growth or stretching of the cells of the lower side of the petiole and central vein, as well as due to corresponding contractions of the tissues of the upper side (raising of leaf blades at night in quinoa, tobacco).

Nyctinasties are motor reactions caused by the onset of darkness, the so-called sleep of plants (closing flowers, lowering the inflorescences of carrots at night).

Photonasty - opening of flower petals when lighting increases (chicory, dandelion, potato inflorescences).

Thermonasty - opening of flowers when the temperature rises (tulip, crocus, coltsfoot, poppy).

Seismonasty - movements of plant organs that are a response to shock or shock (mimosa, sorrel, purslane).

Nutation is the ability of plants to perform circular or pendulum movements due to periodically repeating changes in turgor pressure and the growth rate of opposite sides of a certain organ. Such movements are best expressed at the tops of stems and at the tendrils of climbing plants. Such plants are called climbing or lianas. Among them, according to the method of attachment, they are distinguished curly, tenacious and plants thatintertwined.

U climbing plants During growth, the apex makes uniform nutation movements and, upon contact with a support, begins to wrap around it (hops, morning glory, beans). Tenacious plants have tendrils of different origins, which, twisting or gluing to a support, form a strong and elastic suspension of plants (grapes, bryonia, pumpkin, vetch, peas). Tenacious climbing plants also include those in which sharp hooks or thorns are formed on the stem and leaf petioles (rose hips, wood pliers, Velcro, blackberries), holding the stem to a support.

For plants, which intertwined Characteristic is the placement of lateral branches perpendicular to the main stem, which support the stem on random supports or other plants (raspberries, speedwell, biting midge).

The movements of organs in insectivorous plants (sundew, bladderwrack, Venus flytrap, etc.) are also interesting. The sensitive structures of these plants (glandular hairs, etc.) exceed the sensitivity of the human sense of touch.

The movements that a plant or its organ carries out due to physico-chemical changes in its dead components can be called passive (hygroscopic), since in the absolute majority these movements are caused by changes in the amount of water in the colloids that make up the cell membrane or represent the remains of the cell contents. Most often they are implemented in throwing and moving devices for dispersing fruits and seeds (scales of pine cones, leaves of mature yellow acacia beans, etc.). C. Darwin, Y. Sachs, G. Haberlandt, Jagadis-Chandra Bose, N. G. Kholodny, I. I. Gunar, F. Vent did a lot to understand the processes and mechanisms of plant movement.

Kholodny Nikolai Grigorievich (1882-1953) - Soviet botanist, phytophysiologist and microbiologist, academician. Academy of Sciences of the Ukrainian SSR. Known for his fundamental works on plant physiology and ecology, microbiology and soil science. One of the founders of the doctrine of plant hormones, the author of the hormonal theory of tropisms (known in the literature as the Kholodny-Went theory). The Institute of Botany of the Ukrainian SSR Academy of Sciences is named after him.

The physiological basis for the transmission of irritation in the body of animals is determined by changes in the electrical charge that passes through the cell and releases the hormone, which serves as a connecting bridge between cells, causing changes in permeability in neighboring cells. It is believed that acetylcholine is the carrier of information about irritation.

In plants, the main stimuli are light, chemical compounds, changes in concentration, and the carrier of information is obviously phytohormones, phytochrome and biopotentials.

Almost all types of movements represent a certain reaction of organisms to certain changes in the environment, a reaction aimed at maintaining or creating such conditions and states under which individual organs and the entire organism could best perform their characteristic functions. It was this purposefulness of motor reactions that first drew attention to Charles Darwin.

- Source-

Bogdanova, T.L. Handbook of biology / T.L. Bogdanov [and others]. – K.: Naukova Dumka, 1985.- 585 p.

Post Views: 13

The nervous system regulates the activity of the entire body and its reactions to external and internal changes. One of the functions of nerve cells is irritability.

What is irritability: concept

Irritability is the ability of a living organism to respond to external or internal stimuli. And irritability is a tendency to excessive, inadequate reactions to ordinary environmental stimuli. The causes of irritability may be:

• psychological (fears, anxiety, overwork, alcoholism, high-calorie foods),
• physiological (hormonal changes, lack of certain microelements in the body).

Irritability of organisms

Irritability can manifest itself at all levels of life development. In plants, irritants can be temperature, light, humidity, gravity, and the chemical composition of the environment. A plant, reacting to external or internal stimuli, can develop or die. People and animals are characterized by diverse reactions to different stimuli.

Irritability most often manifests itself in aggression and anger. Irritability is typical for teenagers with their mood swings. In young children, irritability is expressed in restlessness, tearfulness, and the slightest rejection of discomfort. Irritability appears in women during pregnancy due to sudden physiological changes.

Irritability and sensitivity

Sensitivity is the body's reflection of influences that may be necessary or dangerous. Depending on the location of irritation, superficial and deep sensitivity are distinguished.

Superficial sensitivity: pain, temperature (cold, hot), tactile (touch), hair, feeling of moisture, etc. Deep sensitivity: muscle-articular, vibration, sense of weight, sense of pressure.

Irritability and excitability

Excitability is the body's ability to respond with an excitation reaction to irritation. But not every irritation can cause arousal. If irritation occurs slowly and gradually, then excitation may not occur, but with rapid irritation, excitation occurs.

With tissue pathology, excitability can vary from a sharp increase to complete extinction. Sexual excitability is the body's reaction to environmental influences and is associated with pronounced sexual potency.

There is no need to turn irritability into a permanent state of your body. Be healthy!

is the ability of organisms to respond to environmental influences with one or another active reaction. Irritability is a common property of all living organisms.

During evolution, irritability has changed. There was a division of intracellular structures into those that perceive the effects of the stimulus and those that respond to them, and a distinction was made between the processes of irritation as a local reaction and excitation as a spreading reaction in response to the action of the stimulus. Multicellular animals have developed specialized tissues: nervous and muscle, which have adapted to carry out urgent reactions to irritation. The ability of nervous and muscle tissue to quickly respond to stimulation with excitation is called excitability.

In animals, nervous and muscle tissues provide motor and other adaptive reactions, and therefore their systems for receiving and analyzing information (sensory organs) and executive organs (muscles and glands) achieve special development.

Irritability in plants differs significantly from irritability in animals. Plants respond to irritation mainly by changing the speed or direction of growth, the rotational movement of the cytoplasm in the cell and the level of metabolic processes. But there are also plants that have relatively fast motor responses to stimulation. Thus, the tropical plant mimosa pudica folds its leaves in pairs when touched, struck, or at nightfall, and then the entire leaf drops.

IRRITABILITY IRRITABILITY

the ability of living cells, tissues or an entire organism to respond to external influences. or internal influences - irritants; underlies their adaptation to changing environmental conditions. R. manifests itself at all levels of life development and is accompanied by a nonspecific complex. changes, expressed in changes in metabolism, electrical. potential, the state of protoplasm, and in high-level organizations. animals is associated with the implementation of specific. functions (conduction of nerve impulses, muscle contraction, secretion of glandular tissue, etc.). In plants due to structural and functional changes in membranes and underlies their regulatory system. Naib, it is clearly manifested in reactions to light (phototropism, photoperiodism), to gravity. field (geotropism), in engine. reactions (nasty). In animals who do not have a nervous system, reactions to irritations cover the entire protoplasm and are expressed by ch. arr. in the form of an engine reactions (taxis). In multicellular animals, nervous and muscle tissues provide rapid and accurate responses to stimuli; forms of indirect reactive communication with the stimulus develop (reflexively) through higher nervous activity and consciousness. The ability of nerve and muscle cells to respond to stimulation is called. excitability. Sometimes local reactions of tissues or cells are called. reactivity, and the occurrence of a wave-like spreading process - excitability; often the term "R." used as a synonym for excitability.

.(Source: “Biological Encyclopedic Dictionary.” Editor-in-chief M. S. Gilyarov; Editorial Board: A. A. Babaev, G. G. Vinberg, G. A. Zavarzin and others - 2nd ed., corrected . - M.: Sov.

The property of living organisms to respond to various influences (stimuli) with corresponding changes at the level of a cell, tissue or the entire organism. Irritability is associated with the body's adaptation to changing environmental conditions. In plants it manifests itself in reactions to light, gravity, and in motor (as in lower animals) reactions (see. Tropisms, Nastia). Multicellular animals and humans are characterized by more accurate, rapid and varied reactions in response to irritation. They are provided reflexes And higher nervous activity. The term “irritability” is often used as a synonym for “excitability.”

.(Source: “Biology. Modern illustrated encyclopedia.” Chief editor A. P. Gorkin; M.: Rosman, 2006.)

See what “IRRITABILITY” is in other dictionaries:

irritability- a change in the physiological state of the whole organism, its organs, tissues or cells under the influence of external influences called stimuli. The minimum magnitude of the stimulus sufficient to cause such a change is called... ... Great psychological encyclopedia

The ability of living cells, tissues or an entire organism to respond to the influence of factors (stimulants) of the external or internal environment by changing their state or activity. Underlies their adaptation to changing environmental conditions.... ... Ecological dictionary

1) excitability; 2) increasing susceptibility and counter-action in relation to irritation. The historian Lamprecht (“Zur jüngsten deutschen Vergangenheit”, 2 Bde., 1921 – 1922), drawing an analogy with the psychological in the spiritual historical field... ... Philosophical Encyclopedia

IRRITABILITY, irritability, many. no, female (book). distracted noun to irritable; property, ability to be irritated. Nerve irritability. Ushakov's explanatory dictionary. D.N. Ushakov. 1935 1940 ... Ushakov's Explanatory Dictionary

IRRITABILITY- IRRITABILITY, the property of living organisms or their parts to specifically change their states under the influence of changes in the environment or in other parts of the body. Very often the same definition is given to the concept of excitability. There is a big... ... Great Medical Encyclopedia

The property of organisms to respond to environmental influences by changes in their state or activity... Big Encyclopedic Dictionary Synonym dictionary

This article is about the properties of living organisms. For the human trait, see Irritability. Irritability (excitability) is the ability of a living organism to respond to external influences by changing its physicochemical and ... ... Wikipedia